fix: Prevent multiple SessionCache instances from being created. (#2180)

src/Agent/NewRelic/Agent/Core/Agent.cs

@@ -28,8 +28,6 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
-using System.Net.Mime;
-using System.Runtime.InteropServices.ComTypes;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
@@ -65,7 +63,6 @@ public class Agent : IAgent // any changes to api, update the interface in exten
         private readonly ILogEventAggregator _logEventAggregator;
         private readonly ILogContextDataFilter _logContextDataFilter;
         private Extensions.Logging.ILogger _logger;
-        private volatile IStackExchangeRedisCache _stackExchangeRedisCache;
         private readonly ISimpleSchedulingService _simpleSchedulingService;
 
         public Agent(ITransactionService transactionService, ITransactionTransformer transactionTransformer,
@@ -419,11 +416,7 @@ public ISimpleSchedulingService SimpleSchedulingService
             get { return _simpleSchedulingService; }
         }
 
-        public IStackExchangeRedisCache StackExchangeRedisCache
-        {
-            get { return _stackExchangeRedisCache; }
-            set { _stackExchangeRedisCache = value; }
-        }
+        public IStackExchangeRedisCache StackExchangeRedisCache { get; set; }
 
         public void RecordSupportabilityMetric(string metricName, long count = 1)
         {

src/Agent/NewRelic/Agent/Extensions/Providers/Wrapper/StackExchangeRedis2Plus/ConnectWrapperV2.cs

@@ -1,4 +1,4 @@
-// Copyright 2020 New Relic, Inc. All rights reserved.
+// Copyright 2020 New Relic, Inc. All rights reserved.
 // SPDX-License-Identifier: Apache-2.0
 
 using System.Runtime.CompilerServices;
@@ -14,6 +14,7 @@ public class ConnectWrapperV2 : IWrapper
         public bool IsTransactionRequired => false;
 
         private const string WrapperName = "stackexchangeredis-connect";
+        private static readonly object _lock = new();
 
         public CanWrapResponse CanWrap(InstrumentedMethodInfo methodInfo)
         {
@@ -23,22 +24,26 @@ public CanWrapResponse CanWrap(InstrumentedMethodInfo methodInfo)
         public AfterWrappedMethodDelegate BeforeWrappedMethod(InstrumentedMethodCall instrumentedMethodCall, IAgent agent, Agent.Api.ITransaction transaction)
         {
             return Delegates.GetDelegateFor<ConnectionMultiplexer>(
-                onSuccess: muxer =>
-                {
-                    RegisterProfIler(muxer);
-                });
+                onSuccess: RegisterProfiler);
 
-            void RegisterProfIler(IConnectionMultiplexer multiplexer)
+            void RegisterProfiler(IConnectionMultiplexer multiplexer)
             {
                 var xAgent = (IAgentExperimental)agent;
 
                 // The SessionCache is not connection-specific.  This checks for an existing cache and creates one if there is none.
-                if (((IAgentExperimental)agent).StackExchangeRedisCache == null)
+                if (xAgent.StackExchangeRedisCache == null)
                 {
-                    // We only need the hashcode since nothing will change for the methodCall
-                    var hashCode = RuntimeHelpers.GetHashCode(multiplexer);
-                    var sessionCache = new SessionCache(agent, hashCode);
-                    xAgent.StackExchangeRedisCache = sessionCache;
+                    lock (_lock)
+                    {
+                        if (xAgent.StackExchangeRedisCache == null)
+                        {
+                            // We only need the hashcode since nothing will change for the methodCall
+                            var hashCode = RuntimeHelpers.GetHashCode(multiplexer);
+                            var sessionCache = new SessionCache(agent, hashCode);
+
+                            xAgent.StackExchangeRedisCache = sessionCache;
+                        }
+                    }
                 }
 
                 // Registers the profiling function from the shared SessionCache.

src/Agent/NewRelic/Agent/Extensions/Providers/Wrapper/StackExchangeRedis2Plus/SessionCache.cs

@@ -1,4 +1,4 @@
-// Copyright 2020 New Relic, Inc. All rights reserved.
+// Copyright 2020 New Relic, Inc. All rights reserved.
 // SPDX-License-Identifier: Apache-2.0
 
 using System;
@@ -10,6 +10,7 @@
 using NewRelic.Agent.Extensions.Helpers;
 using NewRelic.Agent.Extensions.Parsing;
 using NewRelic.Agent.Extensions.Providers.Wrapper;
+using NewRelic.Core.Logging;
 using NewRelic.Parsing.ConnectionString;
 using StackExchange.Redis.Profiling;
 
@@ -81,10 +82,10 @@ public void Harvest(ISegment hostSegment)
 
         private void CleanUp()
         {
-            var cleanedSessions = 0;
-
             try
             {
+                var cleanedSessions = 0;
+
                 foreach (var pair in _sessionCache)
                 {
                     // This can happen outside the lock since the object transaction was garbage collected.
@@ -107,10 +108,11 @@ private void CleanUp()
                         }
                     }
                 }
+
+                Log.Finest($"SessionCache.Cleanup() removed {cleanedSessions}");
+                _agent.RecordSupportabilityMetric(SessionCacheCleanupSupportabilityMetricName, cleanedSessions);
             }
             catch { } // Don't want to log here, just want to prevent collection problems from breaking things.
-
-            _agent.RecordSupportabilityMetric(SessionCacheCleanupSupportabilityMetricName, cleanedSessions);
         }
 
         private ConnectionInfo GetConnectionInfo(EndPoint endpoint)